The present invention is generally related to endodontic instruments and is more particularly related to an endodontic instrument used to drill an access opening into a pulp chamber of a molar.
A molar includes a crown that projects above a gum line and a root that is secured within a jaw bone. The inside of the molar has a pulp chamber and root canal system through which blood vessels, nerves and connective tissue (hereinafter referred to as “pulp tissue”) extends. The pulp tissue extends from the crown of the tooth to the lower end of the roots where it connects to bone surrounding the root of the tooth.
Frequently, the pulp chamber or root canal of a tooth becomes infected or inflamed. These problems may be caused by repeated dental procedures on the tooth, a crack in the tooth, blunt trauma to the tooth or tooth decay. The symptoms generally associated with an infected or inflamed pulp chamber include sensitivity to heat or cold, swelling and tenderness in the nearby gums, pain and/or discoloration of the tooth. Failure to treat an infected or inflamed pulp chamber may eventually lead to the formation of an abscess and/or cause severe pain.
An endodontic procedure is typically used to treat a tooth having an infected or inflamed pulp chamber. In endodontic therapy, commonly referred to as root canal, a dentist operates on a diseased pulp by removing the diseased pulp tissue and filling in the pulp chamber and the root canal with biocompatible material. Initially, the dentist must gain access to the pulp chamber using a cutting instrument for drilling into the crown of the tooth until the dental instrument reaches the pulp chamber. Dentists typically rely on tactile senses when accessing the pulp chamber. As the dentist drills through dentin, the dentist senses a level of resistance to advancement of the drill, however the level of resistance decreases once the drill reaches the less dense pulp chamber. Once the pulp chamber has been reached, the dentist will remove the diseased pulp tissue from the pulp chamber so as to expose upper ends of the root canals. The dentist may then use a thin, elongated file adapted to fit into the relatively narrow root canals so as to remove all of the pulp tissue from the canals. Once the tissue has been removed from the canals, the dentist irrigates the canals to remove pulpal remnants. Finally, the dentist uses other elongated instruments to widen the root canals and remove irregularities in the canals so that a filling material can be introduced into the canals. Most root canal filling materials comprise biocompatible, thermoplastic material such as gutta purcha.
There have been a number of efforts directed to limiting the depth of penetration of an endodontic instrument into a root canal. For example, U.S. Pat. No. 3,961,422 to Riitano discloses an endodontic file for opening a root canal including a stop for limiting the depth of penetration of the file into the root canal. The '422 patent discloses a bifurcated disk having a central instrument-receiving bore that is made of two disc halves. After the elongated file has been passed through the central bore of the disc, a resilient snap-ring is seated on a circumferential groove surrounding the bifurcated disc to secure the two disc halves of the stop together.
U.S. Pat. No. 6,390,814 to Gardiner discloses another endodontic file having a stop that limits insertion of the file into a root canal.
U.S. Pat. No. 3,962,791 to Zdarsky discloses yet another endodontic file having a stop that limits how far the file can be inserted into the root canal of a tooth. The stop includes a two-part housing having a through-going passage and a compression spring positioned in the passage having an inner diameter that is normally smaller than the outer diameter of the shaft of the file. During assembly, the stop is slipped over the shaft of the root canal file, whereby the compression spring grasps the shaft for preventing sliding of the stop along the shaft. The stop may be slid along the shaft by first rotating the two parts of the housing relative to each other for loosening the spring from the shaft.
When performing a root canal on a molar tooth, a dentist must gain access to the pulp chamber of the molar. Unfortunately, perforations of the furcation of the tooth may occur when accessing the pulp chamber. Typically, a dentist relies on tactile sense when drilling into the pulp chamber of a molar. Generally, the level of resistance is greater when the dentist is drilling through the dentin of the molar, however, the level of resistance is reduced when the drill reaches the pulp chamber. This phenomenon occurs because the density of matter in the pulp chamber is less than the density of the dentin region of the molar. Even though dentists are extremely focused on sensing when the drill transitions from the dentin to the pulp chamber, accidental perforation of the pulp chamber floor and the furcation occur on a regular basis. As is well know to those skilled in the art, a perforation of the furcation of a multi-rooted tooth is a serious complication.
Although the prior art provides numerous endodontic files having stops for limiting penetration of the file into a root canal, the prior art provides no endodontic instruments used to access a pulp chamber of a tooth, whereby the instrument has a stop for preventing perforation of the floor of a pulp chamber or the furcation of a tooth. Thus, there is a need for an endodontic instrument used to drill an access opening into a pulp chamber of a tooth, whereby the instrument has a stop to prevent or limit insertion of the instrument into the tooth. These and other preferred embodiments of the present invention will be described in more detail below.